Method of depositing low K films

ABSTRACT

A silicon oxide layer is produced by plasma enhanced decomposition of an organosilicon compound to deposit films having a carbon content of at least 1% by atomic weight. An optional carrier gas may be introduced to facilitate the deposition process at a flow rate less than or equal to the flow rate of the organosilicon compounds. An oxygen rich surface may be formed adjacent the silicon oxide layer by temporarily increasing oxidation of the organosilicon compound.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/553,461 [AMAT/2592.P3], filed Apr. 19, 2000 now U.S. Pat. No.6,593,247, which is a continuation-in-part of U.S. patent applicationSer. No. 09/021,788 [AMAT/2592], which was filed on Feb. 11, 1998, andis now issued as U.S. Pat. No. 6,054,379 B1, a continuation-in-part ofU.S. patent application Ser. No. 09/114,682 [AMAT/2592.02], which wasfiled on Jul. 13, 1998, and is now issued as U.S. Pat. No. 6,072,227 B1,a continuation-in-part of U.S. patent application Ser. No. 09/162,915[AMAT/3032], which was filed on Sep. 29, 1998; and is now issued as U.S.Pat. No. 6,287,990 B1, and a continuation-in-part of U.S. patentapplication Ser. No. 09/185,555 [AMAT/3032.P1], which was filed on Nov.4, 1998, and is now issued as U.S. Pat. No. 6,303,523, and acontinuation-in-part of U.S. patent application Ser. No. 09/247,381[AMAT/3032.P2], filed on Feb. 10, 1999, and is now issued as U.S. Pat.No. 6,348,725. Each of the aforementioned related patent applications isherein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to the fabrication of integrated circuits.More particularly, the invention relates to a process for depositingdielectric layers on a substrate.

BACKGROUND OF THE INVENTION

One of the primary steps in the fabrication of modern semiconductordevices is the formation of metal and dielectric films on a substrate bychemical reaction of gases. Such deposition processes are referred to aschemical vapor deposition or CVD. Conventional thermal CVD processessupply reactive gases to the substrate surface where heat-inducedchemical reactions take place to produce a desired film. The hightemperatures at which some thermal CVD processes operate can damagedevice structures having layers previously formed on the substrate. Apreferred method of depositing metal and dielectric films at relativelylow temperatures is plasma-enhanced CVD (PECVD) techniques such asdescribed in U.S. Pat. No. 5,362,526, entitled “Plasma-Enhanced CVDProcess Using TEOS for Depositing Silicon Oxide”, which is incorporatedby reference herein. Plasma-enhanced CVD techniques promote excitationand/or disassociation of the reactant gases by the application of radiofrequency (RF) energy to a reaction zone, thereby creating a plasma ofhighly reactive species. The high reactivity of the released speciesreduces the energy required for a chemical reaction to take place, andthus lowers the required temperature for such PECVD processes.

Semiconductor device geometries have dramatically decreased in sizesince such devices were first introduced several decades ago. Sincethen, integrated circuits have generally followed the two year/half-sizerule (often called Moore's Law), which means that the number of devicesthat will fit on a chip doubles every two years. Today's fabricationplants are routinely producing devices having 0.35 μm and even 0.18 μmfeature sizes, and tomorrow's plants soon will be producing deviceshaving even smaller geometries.

In order to further reduce the size of devices on integrated circuits,it has become necessary to use conductive materials having lowresistivity and insulators having low k (dielectric constant<4.0) toreduce the capacitive coupling between adjacent metal lines.Liner/barrier layers have been used between the conductive materials andthe insulators to prevent diffusion of byproducts such as moisture ontothe conductive material. For example, moisture that can be generatedduring formation of a low k insulator readily diffuses to the surface ofthe conductive metal and increases the resistivity of the conductivemetal surface. A barrier/liner layer formed from conventional siliconoxide or silicon nitride materials can block the diffusion of thebyproducts. However, the barrier/liner layers typically have dielectricconstants that are significantly greater than 4.0, and the highdielectric constants result in a combined insulator that does notsignificantly reduce the dielectric constant.

The deposition of silicon oxide films that contain carbon and have lowdielectric constants is described in World Patent Publication No. WO99/41423, which published on Aug. 19, 1999, and is incorporated byreference herein. Films having dielectric constants of about 3.0 or lessare deposited from organosilicon compounds at conditions sufficient todeposit silicon oxide films that contain from 1% to 50% carbon by atomicweight carbon-containing films. Curing of the films to remove moistureimproves the barrier properties of the films. The retention of carbon inthe films contributes to the low dielectric constants. Carbon is morereadily retained in the films at deposition conditions that do not fullyremove moisture from the films, thus, favoring deposition and thencuring of the film. However, films that retain substantial moisture mayshrink and crack during curing which detracts from the smoothness of thefilm or subsequent layers. Process conditions that avoid shrinkage ofthe films are desired.

SUMMARY OF THE INVENTION

The present invention provides a method for depositing a silicon oxidelayer having low moisture content and a low dielectric constant. Thesilicon oxide layer is produced by plasma enhanced decomposition of anorganosilicon compound to deposit films having a carbon content of atleast 1% by atomic weight. Preferably, the plasma is generated at apower density ranging between 0.9 W/cm² and about 3.2 W/cm². An optionalcarrier gas may be introduced to facilitate the deposition process at aflow rate less than or equal to the flow rate of the organosiliconcompounds.

Another aspect of the invention provides for controlling processconditions to deposit a silicon oxide layer having an atomic ratio ofcarbon to silicon (C:Si) of greater than or equal to about 1:9.Preferably the atomic ratio of carbon to silicon (C:Si) is less thanabout 1:1. The silicon oxide layer is produced by plasma enhanceddecomposition of an organosilicon compound, preferably in the presenceof an oxidizing gas and an inert carrier gas.

The silicon oxide layers can replace conventional or low k silicon oxidelayers such as in intermetal dielectric layers, as dielectric layers ina damascene process, or as adhesion layers.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features, advantages andobject of the present invention are attained and can be understood indetail, a more particular description of the invention, brieflysummarized above, may be had by reference to embodiments thereof whichare illustrated in the appended drawings.

It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a cross-sectional diagram of an exemplary CVD plasma reactorconfigured for use according to the present invention;

FIG. 2 is a flow chart of a process control computer program productused in conjunction with the exemplary CVD plasma reactor of FIG. 1; and

FIGS. 3A-3D are cross-sectional views showing an integrated dualdamascene deposition sequence wherein the silicon oxide of the presentinvention is used to eliminate a conventional etch stop.

For a further understanding of the present invention, reference shouldbe made to the ensuing detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is described by reference to a method andapparatus for depositing a silicon oxide layer having a low dielectricconstant and low moisture content. The low moisture content reduces oreliminates curing of the film and enhances surface smoothness, goodhydrophobic properties, a high cracking threshold, and good barrierproperties. The silicon oxide layer is produced by oxidizing anorganosilicon compound which can be used as a dielectric layer, a lininglayer adjacent other dielectric materials, an etch stop layer adjacentother dielectric materials, or as an adhesion layer between differentmaterials. The oxidized organosilicon material is deposited by plasmaassisted oxidation of the organosilicon compounds using a power densityranging between about 0.03 W/cm² and about 3.2 W/cm², which is a RFpower level of between about 10 W and about 1000 W for a 200 mmsubstrate. The silicon oxide layer can be deposited continuously or withinterruptions, such as changing chambers or providing cooling time, toimprove porosity. The RF power is preferably provided at a highfrequency such as between 13 MHz and 14 MHz. The RF power is preferablyprovided continuously or in short duration cycles wherein the power ison at the stated levels for cycles less than about 200 Hz and the oncycles total between about 10% and about 30% of the total duty cycle.

The silicon oxide layer contains carbon which contributes to lowdielectric constants and barrier properties. The remaining carboncontent of the deposited film is between about 1% and about 50% byatomic weight, and is preferably between about 5% and about 30% byatomic weight. The deposited films may contain C—H or C—F bondsthroughout to provide hydrophobic properties to the silicon oxide layerresulting in significantly lower dielectric constants and improvedmoisture barrier properties.

Prior to deposition, reactive process gases are introduced into thechamber. Additionally, an inert gas such as helium may be used in thedeposition to assist in plasma generation. The process gases containingthe organosilicon compounds and the oxidizing gas may be carried by aninert gas, such as He, Ar, Ne, or a relatively inert gas, such asnitrogen, which are typically not incorporated into the film.

In a process where little or no carrier gas is introduced, the oxidationof the process gas deposits a film with low moisture content resultingin less shrinkage during subsequent processing of the film in comparisonto films that retain more moisture. Reduced shrinkage of the filmresults in a smoother surface. The dielectric constant of these filmsshow a range from about 2.6 to about 3.0 depending upon the depositiontemperature. The process temperatures with the limited carrier gassupply is between about 10° C. and about 400° C. Preferably, no carriergas is used in the oxidation reaction, but when a carrier gas is used,the carrier gas will preferably have a flow rate of less than or equalto the flow rate of the process gas containing the organosiliconcompounds.

The silicon oxide layers are produced from organosilicon compoundscontaining carbon in organo groups that are not readily removed byoxidation at processing conditions. Suitable organo groups includealkyl, alkenyl, cyclohexenyl, and aryl groups and functionalderivatives. The organosilicon compounds include:

methylsilane, CH₃—SiH₃ dimethylsilane, (CH₃)₂—SiH₂ trimethylsilane,(CH₃)₃—SiH tetramethylsilane, (CH₃)₄—Si dimethylsilanediol,(CH₃)₂—Si—(OH)₂ ethylsilane, CH₃—CH₂—SiH₃ phenylsilane, C₆H₅—SiH₃diphenylsilane, (C₆H₅)₂—SiH₂ diphenylsilanediol, (C₆H₅)₂—Si—(OH)₃methylphenylsilane, C₆H₅—SiH₂—CH₃ disilanomethane, SiH₃—CH₂—SiH₃bis(methylsilano)methane, CH₃—SiH₂—CH₂—SiH₂—CH₃ 1,2-disilanoethane,SiH₃—CH₂—CH₂—SiH₃ 1,2-bis(methylsilano)ethane, CH₃—SiH₂—CH₂—CH₂—SiH₂—CH₃2,2-disilanopropane, SiH₃—C(CH₃)₂—SiH₃1,3,5-trisilano-2,4,6-trimethylene,

dimethyldimethoxysilane, (CH₃)₂—Si—(OCH₃)₂ diethyldiethoxysilane,(CH₃CH₂)₂—Si—(OCH₂CH₃)₂ dimethyldiethoxysilane, (CH₃)₂—Si—(OCH₂CH₃)₂diethyldimethoxysilane, (CH₃CH₂)₂—Si—(OCH₃)₂ 1,3-dimethyldisiloxane,CH₃—SiH₂—O—SiH₂—CH₃ 1,1,3,3-tetramethyldisiloxane,(CH₃)₂—SiH—O—SiH—(CH₃)₂ hexamethyldisiloxane, (CH₃)₃—Si—O—Si—(CH₃)₃1,3-bis(silanomethylene)disiloxane,

bis(1-methyldisiloxanyl)methane,

2,2-bis(1-methyldisiloxanyl)propane,

2,4,6,8-tetramethylcyclotetrasiloxane,

octamethylcyclotetrasiloxane,

2,4,6,8,10-pentamethylcyclopentasiloxane,

1,3,5,7-tetrasilano-2,6-dioxy-4,8-dimethylene,

2,4,6-trisilanetetrahydropyran, —SiH₂—CH₂—SiH₂—CH₂—SiH₂—O— (cyclic)2,5-disilanetetrahydrofuran, —SiH₂—CH₂—CH₂—SiH₂—O— (cyclic), andfluorinated derivatives thereof.

The organosilicon compounds are oxidized during deposition, preferablyby reaction with oxygen (O₂) or oxygen containing compounds such asnitrous oxide (N₂O), carbon monoxide (CO), carbon dioxide (CO₂), andwater (H₂O), preferably O₂ and N₂O. Organosilicon compounds that containoxygen way be decomposed to provide the oxygen. The deposited film arefurther defined as having an atomic ratio of carbon to silicon (C:Si) inthe film of less than about 1:1. Preferably, the carbon to silicon ratioin the film is between about 1:9 and about 3:4. The deposited filmsformed from oxidized organosilicon compounds have dielectric constantsof less than about 3.0 and low moisture content.

Oxygen and oxygen containing compounds are dissociated to increasereactivity and achieve desired oxidation of the deposited film. RF poweris coupled to the deposition chamber to increase dissociation of theoxidizing compounds. The oxidizing compounds may also be dissociated ina microwave chamber prior to entering the deposition chamber to reduceexcessive dissociation of the organosilicon compounds.

Deposition of the silicon oxide layer can be continuous ordiscontinuous. Although deposition preferably occurs in a singledeposition chamber, the layer can be deposited sequentially in two ormore deposition chambers, e.g., to permit cooling of the film duringdeposition. Furthermore, RF power can be cycled or pulsed to reduceheating of the substrate, which promotes greater porosity in thedeposited film. The oxidizing gas is preferably oxygen which isdisassociated at a power density of at least 0.03 about W/cm². Duringdeposition of the silicon oxide layer, the substrate is maintained at atemperature of between about −20° C. and about 500° C., and preferablyis maintained at a temperature of between about 300° C. and about 450°C.

The organosilicon compounds preferably include the structure:

wherein each Si is bonded to at least two carbon (C) atoms, preferably 2or 3 carbon atoms, and C is included in an organo group, preferablyalkyl or alkenyl groups such as —CH₃, —CH₂—CH₃, —CH₂—, —CH₂—CH₂—, andfluorinated carbon derivatives thereof. The carbon atoms in thefluorinated derivatives may be partially or fully fluorinated to replacehydrogen atoms. When an organosilicon compound includes two or more Siatoms, each Si is separated from another Si by —O—, —C—, or —C—C—,wherein C is included in an organo group, preferably alkyl or alkenylgroups such as —CH₂—, —CH₂—CH₂—, —CH(CH₃)— or —C(CH₃)₂—, or fluorinatedcarbon derivatives thereof.

Preferred organosilicon compounds are gases or liquids near roomtemperature and can be volatilized above about 10 Torr. The preferredorganosilicon compounds include:

dimethylsilane, (CH₃)₂—SiH₂ trimethylsilane, (CH₃)₃—SiHtetramethylsilane, (CH₃)₄—Si dimethylsilanediol, (CH₃)₂—Si—(OH)₂diphenylsilane, (C₆H₅)₂—SiH₂ diphenylsilanediol, (C₆H₅)₂—Si—(OH)₃methylphenylsilane, C₆H₅—SiH₂—CH₃ bis(methylsilano)methane,CH₃—SiH₂—CH₂—SiH₂—CH₃ 1,2-bis(methylsilano)ethane,CH₃—SiH₂—CH₂—CH₂—SiH₂—CH₃ 1,3,5-trisilano-2,4,6- trimethylene,

1,1,3,3-tetramethyldisiloxane, (CH₃)₂—SiH—O—SiH—(CH₃)₂dimethyldimethoxysilane, (CH₃)₂—Si—(OCH₃)₂ diethyldiethoxysilane,(CH₃CH₂)₂—Si—(OCH₂CH₃)₂ dimethyldiethoxysilane, (CH₃)₂—Si—(OCH₂CH₃)₂diethyldimethoxysilane, (CH₃CH₂)₂—Si—(OCH₃)₂ hexamethyldisiloxane,(CH₃)₃—Si—O—Si—(CH₃)₃ trimethylene, octamethylcyclotetrasiloxane,trimethylene,

and fluorinated carbon derivatives thereof, such as:trifluorotrimethylsilane, (CF₃)₃—SiH.

The hydrocarbon groups in the organosilicon compounds may be partiallyor fully fluorinated to convert C—H bonds to C—F bonds. A combination oftwo or more of the organosilicon compounds can be employed to provide ablend of desired properties such as dielectric constant, oxide content,hydrophobicity, film stress, and plasma etching characteristics.

The oxidized compounds adhere to contacted surfaces such as a patternedlayer of a semiconductor substrate to form a deposited film. Thedeposited films may be cured at low pressure and at temperatures frombetween about 100° C. and about 450° C., preferably above about 400° C.,to remove remaining moisture and stabilize the barrier properties of thefilms. The deposited film has sufficient hydrocarbon content to behydrophobic (i.e., repels water) which provides moisture barrierproperties.

Films having low moisture content and low dielectric constants prior tocuring are deposited by oxidizing organosilane compounds having two orthree carbon atoms bonded to each silicon atom at a substratetemperature of between about 10° C. and about 450° C., preferablybetween about 300° C. and about 450° C. The organosilicon compounds areintroduced into a processing chamber maintained at a chamber pressure ofbetween about 200 milliTorr and about 20 Torr, preferably between about2.5 Torr and about 10 Torr, at a flow rate of between about 5 sccm and1000 sccm, preferably at about 600 sccm.

An oxidizing gas may be introduced into the chamber at a flow rate ofless than or equal to about 200 sccm, and preferably at about 100 sccm.More preferably, oxygen is introduced into the chamber at a flow rate ofless than or equal to the flow rate of the organosilicon compounds. Whena carrier gas is used in the deposition process, the carrier gas isintroduced at a flow rate of between about 0 sccm and 2000 sccm,preferably with a flow rate of less than or equal to the flow rate ofthe organosilicon compounds. The reaction is plasma enhanced with apower density ranging between about 0.03 W/cm² and about 3.2 W/cm²,preferably between about 0.9 W/cm² and about 3.2 W/cm². Optionally, abias power having a power density ranging between about 0 W/cm² andabout 1.6 W/cm², e.g., a bias power level of between about 0 watts andabout 500 watts for a 200 mm substrate, preferably at about 250 watts,can be applied during the deposition process to provide improved filingof features formed on a substrate. The bias power promotes even fillingof features such as vias and contact holes by etching the film as it isdeposited.

For producing a low dielectric constant film that has good hydrophobicproperties, and is resistant to cracking, organosilicon compounds areused which will produce films wherein each silicon atom is bonded to atleast one carbon atom, preferably two or three carbon atoms, and eachsilicon atom is bonded to one or two hydrogen atoms.

An oxygen rich surface, or oxide cap, can be formed adjacent the lowdielectric constant film to modify the surface of the film and improveinterlayer adhesion. The oxygen rich surface is formed by exposing theorganosilicon compound deposited on the surface of the low k film tohigher amounts of oxygen. Preferably, an oxygen plasma is formedfollowing deposition of the low k film by terminating the flow of theprecursor while continuing or increasing the oxygen flow. The increasedoxygen replaces additional carbon at the surface of the low k film tofor a silicon oxide layer. Prior to depositing the low dielectricconstant film, an oxygen rich surface can be provided on the underlyingsubstrate surface by depositing the film as described above, except forincreasing the amount of oxygen at the start of the deposition process.The oxygen flow is increased for a time sufficient to remove additionalcarbon from the deposited film and form a silicon oxide layer having lowamounts of carbon.

In an exemplary deposition process for a 200 mm substrate, the oxygenhas a flow rate of less than about 2000 sccm, preferably at a flow rateof about 100 sccm and about 1000 sccm, and most preferably at about 700sccm. The plasma is generated at a power density ranging between about0.03 W/cm² and about 3.2 W/cm², preferably between about 0.9 W/cm² andabout 3.2 W/cm². For a 200 mm substrate, the power density provides fora power level of between about 300 watts and about 1000 watts,preferably at about 600 watts, for a time of between about 5 seconds andabout 60 seconds. The depth of the oxygen rich surface is less thanabout 200 Å, preferably about 150 Å. The temperature of the depositionprocess is maintained at between about 10° C. and about 450° C.,preferably between about 300° C. and about 450° C., with the chamberpressure at between about 200 milliTorr and about 20 Torr, preferablybetween about 2.5 Torr and 10 Torr.

In a preferred embodiment, the oxide rich surface is formed on thedeposited low k film by flowing oxygen at a rate of about 700 sccm intoa chamber maintained at a pressure of about 4 Torr and generating aplasma by applying an RF power of about 600 watts for about thirtyseconds for a 200 mm diameter substrate. It was observed that there wasno adverse impact on the dielectric constant of the deposited low k filmand that the properties of the oxygen rich surface formed on the low kfilm could be further improved by turning off the pump evacuating theprocessing chamber after generating the plasma. It has also beenobserved that the process for forming an oxygen rich surface convertedthe surface of the deposited low k film from hydrophobic (with ameasured wet angle of between about 80° and about 100°) to hydrophilic(with a measured a wet angle of less than 45°), with or without the useof surfactants.

It is contemplated that a film formed from the oxidation reaction has agreater number of oxygen links, —O—, and significantly less Si—H bondsin comparison to films deposited without the disassociated oxygen due tothe presence of more reactive sites in each silicon atom. By minimizingthe number of Si—H bonds in the film, a higher cracking threshold andless moisture uptake can be introduced in a deposited film.Additionally, less Si—H bonding groups make a film more resistant toetching and to oxygen ashing of the film after etching, therebyproviding improved mechanical properties. If desired, enough Si—H bondscan be retained to form subsequent hydrophobic layers.

The deposition process of the present invention can be performed in asubstrate processing system as described in more detail below.

Exemplary CVD Plasma Reactor

FIG. 1 shows a vertical, cross-section view of a parallel plate chemicalvapor deposition reactor 10 having a high vacuum region 15. The reactor10 contains a gas distribution manifold 11 for dispersing process gasesthrough perforated holes in the manifold to a substrate or wafer (notshown) that rests on a substrate support plate or susceptor 12 which israised or lowered by a lift motor 14. A liquid injection system (notshown), such as typically used for liquid injection of TEOS, may also beprovided for injecting a liquid organosilicon compound.

The reactor 10 includes heating of the process gases and substrate, suchas by resistive heating coils (not shown) or external lamps (not shown).Referring to FIG. 1, susceptor 12 is mounted on a support stem 13 sothat susceptor 12 (and the wafer supported on the upper surface ofsusceptor 12) can be controllably moved between a lowerloading/off-loading position and an upper processing position which isclosely adjacent to manifold 11.

When susceptor 12 and the wafer are in processing position 14, they aresurrounded by a an insulator 17 and process gases exhaust into amanifold 24. During processing, gases inlet to manifold 11 are uniformlydistributed radially across the surface of the wafer. A vacuum pump 32having a throttle valve controls the exhaust rate of gases from thechamber.

Before reaching manifold 11, deposition and carrier gases are inputthrough gas lines 18 into a mixing system 19 where they are combined andthen sent to manifold 11. Generally, the process gases supply line 18for each of the process gases also includes (i) safety shut-off valves(not shown) that can be used to automatically or manually shut off theflow of process gas into the chamber, and (ii) mass flow controllers(also not shown) that measure the flow of gas through the gas supplylines. When toxic gases are used in the process, several safety shut-offvalves are positioned on each gas supply line in conventionalconfigurations.

The deposition process performed in reactor 10 can be either a thermalprocess or a plasma enhanced process. In a plasma process, a controlledplasma is typically formed adjacent to the wafer by RF energy applied todistribution manifold 11 from RF power supply 25 (with susceptor 12grounded). Alternatively, RF power can be provided to the susceptor 12or RF power can be provided to different components at differentfrequencies. RF power supply 25 can supply either single or mixedfrequency RF power to enhance the decomposition of reactive speciesintroduced into the high vacuum region 15. A mixed frequency RF powersupply typically supplies power at a high RF frequency (RF1) of 13.56MHz to the distribution manifold 11 and at a low RF frequency (RF2) of360 KHz to the susceptor 12. The silicon oxide layers of the presentinvention are most preferably produced using low levels of constant highfrequency RF power or pulsed levels of high frequency RF power.

When additional dissociation of the oxidizing gas is desired, anoptional microwave chamber 28 can be used to input from between about 0Watts and about 6000 Watts of microwave power to the oxidizing gas priorto entering the deposition chamber. Separate addition of microwave powerwould avoid excessive dissociation of the organosilicon compounds priorto reaction with the oxidizing gas. A gas distribution plate havingseparate passages for the organosilicon compound and the oxidizing gasis preferred when microwave power is added to the oxidizing gas.

Typically, any or all of the chamber lining, distribution manifold 11,susceptor 12, and various other reactor hardware is made out of materialsuch as aluminum or anodized aluminum. An example of such a CVD reactoris described in U.S. Pat. No. 5,000,113, entitled A Thermal CVD/PECVDReactor and Use for Thermal Chemical Vapor Deposition of Silicon Dioxideand In-situ Multi-step Planarized Process, issued to Wang et al. andassigned to Applied Materials, Inc., the assignee of the presentinvention.

The lift motor 14 raises and lowers susceptor 12 between a processingposition and a lower, wafer-loading position. The motor, the gas mixingsystem 19, and the RF power supply 25 are controlled by a systemcontroller 34 over control lines 36. The reactor includes analogassemblies, such as mass flow controllers (MFCs) and standard or pulsedRF generators, that are controlled by the system controller 34 whichexecutes system control software stored in a memory 38, which in thepreferred embodiment is a hard disk drive. Motors and optical sensorsare used to move and determine the position of movable mechanicalassemblies such as the throttle valve of the vacuum pump 32 and motorfor positioning the susceptor 12.

The system controller 34 controls all of the activities of the CVDreactor and a preferred embodiment of the controller 34 includes a harddisk drive, a floppy disk drive, and a card rack. The card rack containsa single board computer (SBC), analog and digital input/output boards,interface boards and stepper motor controller boards. The systemcontroller conforms to the Versa Modular Europeans (VME) standard whichdefines board, card cage, and connector dimensions and types. The VMEstandard also defines the bus structure having a 16-bit data but and24-bit address bus.

The system controller 34 operates under the control of a computerprogram stored on the hard disk drive 38. The computer program dictatesthe timing, mixture of gases, RF power levels, susceptor position, andother parameters of a particular process.

Referring to FIG. 2, the process can be implemented using a computerprogram product 410 that runs on, for example, the system controller 34.The computer program code can be written in any conventional computerreadable programming language such as for example 68000 assemblylanguage, C, C++, or Pascal. Suitable program code is entered into asingle file, or multiple files, using a conventional text editor, andstored or embodied in a computer usable medium, such as a memory systemof the computer. If the entered code text is in a high level language,the code is compiled, and the resultant compiler code is then linkedwith an object code of precompiled windows library routines. To executethe linked compiled object code, the system user invokes the objectcode, causing the computer system to load the code in memory, from whichthe CPU reads and executes the code to perform the tasks identified inthe program.

FIG. 2 shows an illustrative block diagram of the hierarchical controlstructure of the computer program 410. A user enters a process setnumber and process chamber number into a process selector subroutine 420in response to menus or screens displayed on the CRT monitor 40 by usingthe light pen 44 interface. The process sets are predetermined sets ofprocess parameters necessary to carry out specified processes, and areidentified by predefined set numbers. The process selector subroutine420 the (i) selects a desired process chamber on a cluster tool such asan Centura® platform (available from Applied Materials, Inc.), and (ii)selects a desired set of process parameters needed to operate theprocess chamber for performing the desired process. The processparameters for performing a specific process relate to processconditions such as, for example, process gas composition and flow rates,temperature, pressure, plasma conditions such as RF bias power levelsand magnetic field power levels, cooling gas pressure, and chamber walltemperature and are provided to the user in the form of a recipe. Theparameters specified by the recipe are entered utilizing the lightpen/CRT monitor interface.

The signals for monitoring the process are provided by the analog inputand digital input boards of system controller and the signals forcontrolling the process are output on the analog output and digitaloutput boards of the system controller 34.

A process sequencer subroutine 430 comprises program code for acceptingthe identified process chamber and set of process parameters from theprocess selector subroutine 420, and for controlling operation of thevarious process chambers. Multiple users can enter process set numbersand process chamber numbers, or a user can enter multiple processchamber numbers, so the sequencer subroutine 430 operates to schedulethe selected processes in the desired sequence. Preferably the sequencersubroutine 430 includes computer readable program code to perform thesteps of (i) monitoring the operation of the process chambers todetermine if the chambers are being used, (ii) determining whatprocesses are being carried out in the chambers being used, and (iii)executing the desired process based on availability of a process chamberand type of process to be carried out. Conventional methods ofmonitoring the process chambers can be used, such as polling. Whenscheduling which process is to be executed, the sequencer subroutine 430can be designed to take into consideration the present condition of theprocess chamber being used in comparison with the desired processconditions for a selected process, or the “age” of each particular userentered request, or any other relevant factor a system programmerdesires to include for determining the scheduling priorities.

Once the sequencer subroutine 430 determines which process chamber andprocess set combination is going to be executed next, the sequencersubroutine 430 causes execution of the process set by passing theparticular process set parameters to a chamber manager subroutine 440which controls multiple processing tasks in a process chamber 10according to the process set determined by the sequencer subroutine 430.For example, the chamber manager subroutine 440 comprises program codefor controlling CVD process operations in the process chamber 10. Thechamber manager subroutine 440 also controls execution of variouschamber component subroutines which control operation of the chambercomponent necessary to carry out the selected process set. Examples ofchamber component subroutines are susceptor control subroutine 450,process gas control subroutine 460, pressure control subroutine 470,heater control subroutine 480, and plasma control subroutine 490. Thosehaving ordinary skill in the art would readily recognize that otherchamber control subroutines can be included depending on what processesare desired to be performed in the reactor 10.

In operation, the chamber manager subroutine 440 selectively schedulesor calls the process component subroutines in accordance with theparticular process set being executed. The chamber manager subroutine440 schedules the process component subroutines similarly to how thesequencer subroutine 430 schedules which process chamber 10 and processset is to be executed next. Typically, the chamber manager subroutine440 includes steps of monitoring the various chamber components,determining which components needs to be operated based on the processparameters for the process set to be executed, and causing execution ofa chamber component subroutine responsive to the monitoring anddetermining steps.

Operation of particular chamber component subroutines will now bedescribed with reference to FIG. 2. The susceptor control positioningsubroutine 450 comprises program code for controlling chamber componentsthat are used to load the substrate onto the susceptor 12, andoptionally to lift the substrate to a desired height in the reactor 10to control the spacing between the substrate and the gas distributionmanifold 11. When a substrate is loaded into the reactor 10, thesusceptor 12 is lowered to receive the substrate, and thereafter, thesusceptor 12 is raised to the desired height in the chamber, to maintainthe substrate at a first distance or spacing from the gas distributionmanifold 11 during the CVD process. In operation, the susceptor controlsubroutine 450 controls movement of the susceptor 12 in response toprocess set parameters that are transferred from the chamber managersubroutine 440.

The process gas control subroutine 460 has program code for controllingprocess gas composition and flow rates. The process gas controlsubroutine 460 controls the open/close position of the safety shut-offvalves, and also ramps up/down the mass flow controllers to obtain thedesired gas flow rate. The process gas control subroutine 460 is invokedby the chamber manager subroutine 440, as are all chamber componentssubroutines, and receives from the chamber manager subroutine processparameters related to the desired gas flow rates. Typically, the processgas control subroutine 460 operates by opening the gas supply lines, andrepeatedly (i) reading the necessary mass flow controllers, (ii)comparing the readings to the desired flow rates received from thechamber manager subroutine 440, and (iii) adjusting the flow rates ofthe gas supply lines as necessary. Furthermore, the process gas controlsubroutine 460 includes steps for monitoring the gas flow rates forunsafe rates, and activating the safety shut-off valves when an unsafecondition is detected.

In some processes, an inert gas such as helium or argon is flowed intothe reactor 10 to stabilize the pressure in the chamber before reactiveprocess gases are introduced into the chamber. For these processes, theprocess gas control subroutine 460 is programmed to include steps forflowing the inert gas into the chamber 10 for an amount of timenecessary to stabilize the pressure in the chamber, and then the stepsdescribed above would be carried out. Additionally, when a process gasis to be vaporized from a liquid precursor, for example1,3,5-trisilano-2,4,6-trimethylene (1,3,5-trisilanacyclo-hexane), theprocess gas control subroutine 460 would be written to include steps forbubbling a delivery gas such as helium through the liquid precursor in abubbler assembly. For this type of process, the process gas controlsubroutine 460 regulates the flow of the delivery gas, the pressure inthe bubbler, and the bubbler temperature in order to obtain the desiredprocess gas flow rates. As discussed above, the desired process gas flowrates are transferred to the process gas control subroutine 460 asprocess parameters. Furthermore, the process gas control subroutine 460includes steps for obtaining the necessary delivery gas flow rate,bubbler pressure, and bubbler temperature for the desired process gasflow rate by accessing a stored table containing the necessary valuesfor a given process gas flow rate. Once the necessary values areobtained, the delivery gas flow rate, bubbler pressure and bubblertemperature are monitored, compared to the necessary values and adjustedaccordingly.

The pressure control subroutine 470 comprises program code forcontrolling the pressure in the reactor 10 by regulating the size of theopening of the throttle valve in the exhaust pump 32. The size of theopening of the throttle valve is set to control the chamber pressure tothe desired level in relation to the total process gas flow, size of theprocess chamber, and pumping set point pressure for the exhaust pump 32.When the pressure control subroutine 470 is invoked, the desired, ortarget pressure level is received as a parameter from the chambermanager subroutine 440. The pressure control subroutine 470 operates tomeasure the pressure in the reactor 10 by reading one or moreconventional pressure manometers connected to the chamber, compare themeasure value(s) to the target pressure, obtain PID (proportional,integral, and differential) values from a stored pressure tablecorresponding to the target pressure, and adjust the throttle valveaccording to the PID values obtained from the pressure table.Alternatively, the pressure control subroutine 470 can be written toopen or close the throttle valve to a particular opening size toregulate the reactor 10 to the desired pressure.

The heater control subroutine 480 comprises program code for controllingthe temperature of the heat modules or radiated heat that is used toheat the susceptor 12. The heater control subroutine 480 is also invokedby the chamber manager subroutine 440 and receives a target, or setpoint, temperature parameter. The heater control subroutine 480 measuresthe temperature by measuring voltage output of a thermocouple located ina susceptor 12, compares the measured temperature to the set pointtemperature, and increases or decreases current applied to the heatmodule to obtain the set point temperature. The temperature is obtainedfrom the measured voltage by looking up the corresponding temperature ina stored conversion table, or by calculating the temperature using afourth order polynomial. The heater control subroutine 480 graduallycontrols a ramp up/down of current applied to the heat module. Thegradual ramp up/down increases the life and reliability of the heatmodule. Additionally, a built-in-fail-safe mode can be included todetect process safety compliance, and can shut down operation of theheat module if the reactor 10 is not properly set up.

The plasma control subroutine 490 comprises program code for setting theRF bias voltage power level applied to the process electrodes in thereactor 10, and optionally, to set the level of the magnetic fieldgenerated in the reactor. Similar to the previously described chambercomponent subroutines, the plasma control subroutine 490 is invoked bythe chamber manager subroutine 440.

The above CVD system description is mainly for illustrative purposes,and other plasma CVD equipment such as electrode cyclotron resonance(ECR) plasma CVD devices, induction-coupled RF high density plasma CVDdevices, or the like may be employed. Additionally, variations of theabove described system such as variations in susceptor design, heaterdesign, location of RF power connections and others are possible. Forexample, the wafer could be supported and heated by a resistively heatedsusceptor. The pretreatment and method for forming a pretreated layer ofthe present invention is not limited to any specific apparatus or to anyspecific plasma excitation method.

Dual Damascene Integration

FIGS. 3A-3D are cross sectional views of a substrate showing underlyinglayers following sequential steps in a dual damascene process. The dualdamascene structure 800 comprises silicon oxide layers having lowdielectric constants to reduce cross-talk between metal lines.

As shown in FIG. 3A, a first or via level dielectric layer 810 isdeposited and pattern etched on the substrate 812. The via leveldielectric layer can be deposited on the substrate 812 by conventionalmeans known in the art, but is preferably deposited by oxidizing one ormore organosilicon compounds at a RF power density of at least about0.03 W/cm² to deposit a silicon oxide film having a carbon content of atleast 1% by atomic weight. The via level dielectric layer 810 preferablyhas a carbon content of about 20 percent by atomic weight, and isdeposited to a thickness of between about 5,000 and about 10,000 Å,depending on the size of the structure to be fabricated. The via leveldielectric layer is preferably deposited by reacting O₂ andtrimethylsilane at an RF power level of about 600 W for a 200 mmdiameter substrate with a chamber pressure of about 4 Torr and asubstrate temperature of about 350° C. Once deposited, the via leveldielectric layer is then pattern etched to form the vias and contactholes 814 with photolithography and etch processes for silicon oxidefilms using fluorine, carbon, and oxygen ions.

As shown in FIG. 3B, a second, or trench level dielectric layer 822comprises a silicon oxide layer deposited by oxidizing one or moreorganosilicon compounds at a RF power density of at least about 0.03W/cm² to produce a film having a carbon content of at least 1% by atomicweight. The trench level dielectric layer 822 preferably has a carboncontent of about 10% by atomic weight, and is deposited over the vialevel dielectric layer 810 to a thickness of between about 5,000 andabout 10,000 Å. The trench level dielectric layer is preferablydeposited by reacting O₂ and dimethylsilane at an RF power level ofabout 600 W for a 200 mm diameter substrate with a chamber pressure ofabout 4 Torr and a substrate temperature of about 350° C. The trenchlevel dielectric layer 822 is then pattern etched to define interconnectlines 824 as shown in FIG. 3B, using photolithography processes and etchprocesses. The etch process used for the trench level dielectric layersis preferably more effective for silicon oxides having lower carboncontents to reduce over-etching of the via level dielectric layer. Anyphoto resist or other material used to pattern the dielectric layers isremoved using chemical mechanical polishing, an oxygen strip, or othersuitable process.

The metallization structure is then formed with a conductive materialsuch as aluminum, copper, tungsten or combinations thereof. Presently,the trend is to use copper to form the smaller features due to the lowresistivity of copper compared to aluminum. Preferably, as shown in FIG.3C, a suitable barrier layer 828 such as tantalum nitride is firstdeposited conformally in the metallization pattern to prevent coppermigration into the surrounding silicon and/or dielectric material.Thereafter, copper 830 is deposited as shown in FIG. 4D using eitherchemical vapor deposition, physical vapor deposition, electroplating, orcombinations thereof to form the conductive structure. Once thestructure has been filled with copper or other metal, the surface isplanarized using chemical mechanical polishing or other planarizingmethods.

In an alternative embodiment of a dual damascene structure (not shown),both the via level and the trench level dielectric layers could containessentially the same amount of carbon, e.g., about 10% carbon by atomicweight, if separated by an etch stop layer that contains a differentamount of carbon, e.g., about 20% carbon by atomic weight. The etch stoplayer would be pattern etched to define the vias and contact holes asdescribed above.

Referring to FIGS. 3A-3D, the dielectric layers 810, 812 are depositedin the reactor 10 by introducing an oxidizing gas, preferably O₂, anorganosilicon compound, such as (CH₃)₃SiH, (CH₃)₂SiH₂, or combinationsthereof, and a carrier gas, such as helium. The substrate is maintainedat a temperature between about −20° C. and about 500° C., and preferablyis maintained at a temperature of approximately 300° C. to 450° C.,throughout the deposition of the dielectric layer. The dielectric layeris deposited with a process gas that includes a mixture of theorganosilicon compound at a flow rate of between about 5 sccm and about1000 sccm and the oxidizing gas at a flow rate of less than about 200sccm. In depositing layers with a smooth surface and low dielectricconstants, the carrier gas typically has a flow rate less than or equalto the flow rate of the process gas that includes a mixture of theorganosilicon compound. In this instance, the carrier gas has a flowrate of between about 0 sccm and about 1000 sccm. The carrier gas isoptional, since the process gas oxidation reaction can occur in thetotal absence of a carrier gas to deposit a smooth surface dielectriclayer.

The process gases react at a pressure from between about 0.2 and about20 Torr, preferably between about 2.5 Torr and about 10 Torr, to form aconformal silicon oxide layer. Generally, it has been observed that ahigher deposition pressure will produce films with lower dielectricconstants, or higher carbon contents, but such a trend may not be truefor all identified precursors under the identified processingparameters.

The process temperature range is preferably between about 10° C. andabout 450° C. for depositing layers with a smooth surface and a lowdielectric constant (k 2.6-3.0). The dielectric constant depends uponthe process temperature with a lower temperature generally producing alower dielectric constant. The reaction is plasma enhanced with a powerdensity ranging between about 0.03 W/cm² and about 3.2 W/cm². It hasbeen further observed that the lower dielectric films can be produced atlower power rates.

For an 8″ single wafer chamber, the high frequency RF source ofapproximately 13.56 MHz is preferably connected to a gas distributionsystem and driven at between about 10 and about 1000 W while a lowfrequency RF source of about 350 KHz to 1 MHz is optionally connected toa susceptor and driven at between about 0 W and about 500 W. In apreferred embodiment, the high frequency RF source is driven at betweenabout 300 W and about 1000 W of continuous or pulsed RF power, and thelow frequency RF source is driven at about 0 and about 50 W of pulsed RFpower at a duty cycle from 10% to 30% for a 200 mm diameter substrate.The pulsed RF power is preferably cycled in short intervals, mostpreferably having a frequency less than about 200 Hz.

The oxidized organosilicon layer may be cured at a pressure less thanabout 10 Torr a temperature from between about 100° C. and about 450° C.Optionally, curing could be conducted after deposition of additionaldielectric layers.

The above process conditions result in the deposition of a dielectriclayer (at about 2000 Å per minute) with good hydrophobic properties,good resistance to cracking, and improved barrier characteristics forsubsequently deposited layers. The deposited dielectric layers have aWith the limited carrier gas flow rate, the deposited layer 300 has alow dielectric, typically 2.6 to 3.0 and has a smooth surface which isbeneficial to the deposition of subsequent layers and etching processes.The lining layer obtained from trimethylsilane has sufficient C—H bondsto be hydrophobic, and is an excellent moisture barrier. Deposition of ahydrophobic lining layer has a surprising and unexpected result ofconverting subsequent hydrophilic layers to hydrophobic layers.Additionally, by limiting an oxidizing gas in the oxidation reaction, afilm can be produced with a lower amount of Si—H bonds that has a highcracking threshold while still retaining the desired hydrophobicproperties.

Preferred organosilicon compounds containing carbon of the invention mayalso be used as a gap filling layer over the etch stop in place of thedielectric films deposited by the process detailed above. The processgases for the gap filling layer are preferably (CH₃)₂SiH₂ and 50 wt. %of hydrogen peroxide (H₂O₂) which is vaporized and mixed with an inertcarrier gas, such as helium. Alternative organosilicon compounds can beused if byproducts are vapors at deposition conditions. Preferredalternative compounds incorporate oxysilano or silano groups, such as:

trimethylsilane,

disilanomethane,

bis(methylsilano)methane,

1,2-disilanoethane,

2,2-disilanopropane,

1,3,5-trisilano-2,4,6-trimethylene (cyclic),

1,3-bis(silanomethylene)siloxane,

bis(1-methyldisiloxanyl)methane,

2,4,6,8-tetramethylcyclotetrasiloxane, or

1,2-disilanotetrafluoroethane.

The process gas flows range from between about 0 and about 2000 sccm forHe, between about 10 and about 200 sccm for CH₃SiH, and between about0.1 and about 3 g/min. for H₂O₂. The preferred gas flows range frombetween about 100 and about 500 sccm for He, between about 20 and about100 sccm for CH₃SiH, and between about 0.1 and about 1 g/min. for H₂O₂.These flow rates are given for a chamber having a volume ofapproximately between about 5.5 and about 6.5 liters.

The invention is further described by the following examples.

EXAMPLES

The following examples demonstrate the deposition of oxidizedorganosilicon films having smooth surfaces, good hydrophobic properties,high cracking thresholds, and low dielectric constants on 200 mmdiameter substrates. This example was undertaken using a chemical vapordeposition chamber, and in particular, a “CENTURA DxZ” system whichincludes a solid-state RF matching unit with a two-piece quartz processkit, both fabricated and sold by Applied Materials, Inc., Santa Clara,Calif.

Example of Low Dielectric Constant Film with Smooth Surface

An oxidized trimethylsilane film was deposited at a chamber pressure of4.0 Torr and a temperature of 350° C. from reactive gases which wereflowed into the reactor as follows:

Trimethylsilane, (CH₃)₃SiH, at 600 sccm Oxygen, O₂, at 100 sccm Helium,He, at   0 sccm

The substrate was positioned 220 millimeters from the gas distributionshowerhead and 600 W of high frequency power (13.56 MHz) was applied tothe showerhead for plasma enhanced deposition of an oxidizedtrimethylsilane layer at an observed rate of about 7000 Å/minute. Theoxidized trimethylsilane material had a dielectric constant of about2.8+/−0.1, a carbon content of about 17%, a thickness uniformity of lessthan about 3%, and was hydrophobic. The deposited film indicated a RMS(root-mean-square) thickness of 5 Å and a R_(max) (peak to valley)distance of 75 Å, which is less than the observed 60 Å RMS and 500 ÅR_(max) in films deposited with a carrier gas. The data from the sampledielectric layers indicate the films of the present invention have muchsmoother surfaces than prior techniques. Dielectric constantmeasurements of films produced under the above processing conditionsshow a dielectric constant range of about 2.6 to 3.0 depending upon thedeposition temperatures.

Example of High Cracking Threshold and Low Dielectric Constant

An oxidized trimethylsilane film was deposited at a chamber pressure of4 Torr and a temperature of 350° C. from reactive gases which wereflowed into the reactor as follows:

Trimethylsilane, (CH₃)₃SiH, at 600 sccm Oxygen, O₂, at 100 sccm Helium,He, at  0 sccm

The substrate was positioned 220 millimeters from the gas distributionshowerhead and 600 W of high frequency power 13.56 MHz was applied tothe showerhead for plasma enhanced deposition of an oxidizedtrimethylsilane layer at an observed rate of about 7000 Å/minute. Theoxidized trimethylsilane material had a dielectric constant of about2.8+/−0.1, a thickness uniformity of about less than about 3%, and washydrophobic.

While the foregoing is directed to preferred embodiments of the presentinvention, other and further embodiments of the invention may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims which follow.

What is claimed is:
 1. A process for depositing a low dielectricconstant film, comprising decomposing one or more organosiliconcompounds selected from a group consisting ofoctamethylcyclotetrasiloxane, hexamethyldisiloxane,bis(1-methyldisiloxanyl)methane,2,4,6,8,10-pentamethylcyclopentasiloxane,1,3,5,7-tetrasilano-2,6-dioxy-4,8-dimethylene,2,4,6-trisilanetetrahydropyran, and 2,5-disilanetetrahydrofuran at a RFpower density of at least about 0.03 W/cm² and at a processing chamberpressure of between about 0.2 Torr and about 20 Torr to deposit a filmcomprising silicon, oxygen, and a carbon content of at least 1% byatomic weight.
 2. The process of claim 1, wherein the low dielectricconstant film has an atomic ratio of carbon to silicon (C:Si) of lessthan about 1:1.
 3. The process of claim 1, wherein the low dielectricconstant film has an atomic ratio of carbon to silicon (C:Si) betweenabout 1:4 and about 3:4.
 4. The process of claim 1, wherein the one ormore organosilicon compounds have a flow rate of between about 5 sccmand about 1000 sccm.
 5. The process of claim 1, wherein the one or moreorganosilicon compounds are decomposed in the presence of a carrier gas.6. The process of claim 1, wherein the one or more organosiliconcompounds comprise octamethylcyclotetrasiloxane.
 7. The process of claim1, wherein the low dielectric constant film is deposited at atemperature of between about 10° C. and about 500° C.
 8. The process ofclaim 5, wherein the carrier gas has a flow rate less than or equal to acombined flow rate of the one or more organosilicon compounds.
 9. Theprocess of claim 1, further comprising forming an oxide rich surfaceadjacent the low dielectric constant film.
 10. A process for depositinga low dielectric constant film, consisting essentially of decomposingone or more organosilicon compounds selected from the group consistingof octamethylcyclotetrasiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane,1,3-dimethyldisiloxane, 1,1,3,3-tetramethyldisiloxane,hexamethyldisiloxane,1,3-bis(silanomethylene)disiloxane,bis(1-methyldisiloxanyl)methane, 2,2-bis(1-methyldisiloxanyl)propane,2,4,6,8,10-pentamethylcyclopentasiloxane,1,3,5,7-tetrasilano-2,6-dioxy-4,8-dimethylene,2,4,6-trisilanetetrahydropyran, and 2,5-disilanetetrahydrofuran at apower density of greater than about 0.03 W/cm² and at a processingchamber pressure of between about 0.2 Torr and about 20 Torr, and acarrier gas flow rate less than or equal to a combined flow rate of theone or more organosilicon compounds at conditions sufficient to deposita film comprising silicon, oxygen, and carbon and an atomic ratio ofcarbon to silicon (C:Si) of greater than or equal to about 1:9.
 11. Theprocess of craim 10, wherein the atomic ratio of carbon to silicon(C:Si) is less than about 1:1 in the film.
 12. The process of claim 10,wherein the atomic ratio of carbon to silicon (C:Si) is between about1:4 and about 3:4 in the film.
 13. The process of claim 10, wherein theone or more organosilicon compounds compriseoctamethylcyclotetrasiloxane.
 14. The process of claim 10, furthercomprising forming an oxide rich surface adjacent the low dielectricconstant film.
 15. A process for depositing a low dielectric constantfilm, comprising decomposing octamethylcyclotetrasiloxane at a powerdensity ranging between about 0.9 W/cm² and about 3.2 W/cm² and at aprocessing chamber pressure of between about 0.2 Torr and about 20 Torrto deposit a film having an atomic ratio of carbon to silicon (C:Si) ofbetween about 1:9 and about 1:1.
 16. The process of claim 15, whereinthe atomic ratio of carbon to silicon (C:Si) is between about 1:4 andabout 3:4 in the film.
 17. The process of claim 15, wherein the lowdielectric constant film is deposited at a temperature of between about300° C. and about 450° C.
 18. The process of claim 15, wherein the lowdielectric constant film is deposited at a processing chamber pressureof between about 2.5 Torr and about 10 Torr.
 19. The process of claim15, further comprising a carrier gas having a flow rate less than orequal to a flow rate of the octamethylcyclotetrasiloxane.
 20. Theprocess of claim 15, further comprising forming an oxide rich surfaceadjacent the low dielectric constant film.